Selco Seal

Abstract

People have been trying to stop leaks since recorded history began. Whether we talk about stopping a leaking roof, sealing a Roman aqueduct, or caulking an Egyptian barge, a way has been found to stop leaks, or at least stem the tide. Until the Industrial Revolution water was the common target of the “leak stoppers”. With the invention of the steam power pump, and its application to rail and water locomotion and factory power, came the added difficulties of sealing against heat and pressure. Use was made of brass and iron for pipes and vessels but the higher heat caused impurities to clog the system, so the Bolted Flange was invented to facilitate assembly and disassembly. The joints were packed with asbestos, one of the few materials that could handle the temperatures involved and still have the compressibility and resilience to form a seal. Richard Klinger added Rubber to the asbestos in the 1890’s. The addition of the rubber greatly enhanced the performance of seals because it filled the voids and added resilience. But higher and higher pressures in excess of 4000 psi and temperatures in excess of 1000 degrees Fahrenheit required more from a gasket. This led to the development of the Spiralwound gasket in the mid 20th century. Concurrently, many additional gasket materials were developed to handle the many chemicals from the technology explosion after WWII. Then almost overnight asbestos was to be eliminated because of the health hazards. At the same time tougher environmental regulations required better gaskets. Fortunately, just as asbestos was to be eliminated, Flexible Graphite was coming into prominence. Flexible Graphite is a superior sealing material with a wide temperature range, better compressibility and recovery characteristics, but is subject to cold flow and erosion by the media. The Gasket incorporates Flexible Graphite in containment grooves in the metal carrier. This combination provides a high unit load for easy in sealing, protection for the fragile Flexible Graphite, while utilizing the cold flow properties to provide superior sealing.